Concurrent flow drier with rotor, stationary casing, and terminal separation means for drying materials and drying fluid



Jan. 25, 1949. o HELLER 2,460,008

CONCURRENT FLOW DRIER WITH "ROTOR, STATIONARY CASING AND TERMINAL SEPARATION MEANS FOR DRYING MATERIALS AND DRYING FLUID Filed Nov. 13, 1944 V '3 Sheets+Sheet l Y 2 {1/45 2s I II l| 6 Iii a:

lggenfor Jan. 25, 194 9. HELLER 2,460,008

' CONCURRENT FLOW DRIER WITH ROTOR, STATIONARY CASING AND TERMINAL SEPARATION MEANS FOR DRYING MATERIALS AND DRYING FLUID 3 Sheets-Sheet 2 Filed Nov. 13, 1944 lnvenlof:

Jan. 25, 1949. o. HELLER 2,460,008

CONCURRENT FLOW DRIER WITH ROTOR, STATIONARY I CASING AND TERMINAL SEPARATION MEANS FOR DRYING MATERIALS AND DRYING FLUID Filed-Nov. 13, 1944 3 Sheets-Sheet 3 I [n0 r llor: Y

I Allorneya.

' tion to their mass.

' Patented 25,1949

STATIONARY CASING,

AND TERMINAL SEPARATION MEANS FOR DRYING MATE- RIALS AND DRYING FLUID Oswald Heller, London, England, assignor to Bamag, Limited, London, England, a company of Great Britain and Northern Ireland Application November 13, 1944, Serial No. 563,160 In Great Britain October 23, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires October 23, 1963 This invention relates to drying apparatus, and has for an object to combine the advantages of the so-called pneumatic dryer with the compactness of the substantially horizontal drum type dryer. v

In the known forms of pneumatic dryers in which the substance to be dried is carried in .a stream of hot gases through a system of drying chambers and ducts, the gases must have a lineal speed high enough to carry the substance to be dried and to hold it in suspension; Therefore, the path of the gas-borne material must be long in order to get the necessary drying time, and consequently all such plants have very great dimensions and are liable to extensive heat losses from their surfaces.

Such dryers, therefore, are only suitable for materials having a short drying time, that is, materials having an extensive surface area in rela- Where some at least of the wet material is dense or relatively bulky, after the initial intensive drying stage it is usual to provide separating means by which the still wet and heavier particles are returned to the hot gas system after'passing through bruising, crushing, distintegrating or like means outside the hot gas stream, which means serve to expose fresh moist surfaces to the gases.

- Pneumatic dryers in general have the advantage of a quick and intensive drying effect which is due to the fact that the wholesurface of the substance to be dried is continuously exposed to the drying gases, so that evaporation of the moisture content is rapid, in fact almost instantaneous, and gases having a very high initial temperature can be employed. Thereafter, of course, the rate of drying decreases since the relative speed of the substance and the gases transporting them is small, and the temperature difference is reduced to a degree which the material can tolerate without deterioration.

Aiurther advantage of the pneumatic dryer is the possibility of segregation of lighter and heavier (for example, dried and partly dried) elements as in a gravity separating chamber in the drying system.

In the horizontal drum type dryer, on the other hand, whether of the type having a rotating drum with lifting devices or of the type havinga stationary drum with rotating agitators, the bulk of the material to be dried lies at the bottom of the drum in a thick mass of which only a small proportion is exposed to the hot gases. Even the lifting devices of a rotary drum carry compact layers of material, and the proportion of the dry- Claims. (Cl. 241-38) ing time during which the elements of' material are actually falling from the lifters, and so wholly exposed to the hot gases, is very small. Thus the drying effect is less than would be the case if the whole surface of the material elements were continuously exposed to the gases.

The present invention provides an improved pneumatic dryer construction, having the advantage that the material is carried by and fully exposed to the drying gases in an involved path so that, for the several operations of drying (including if necessary cutting or breaking of the larger material elements), separating fully dried from partly dried material elements, and separating dried material from the gases, the space required is reduced to a minimum and confined within a single envelope, and the thermal efiiciency is enhanced.

Drying apparatus according to this invention comprises an envelope of substantially circular cross-section along the inside of which envelope material is carried in helical flow and is subjected to heat exchange with hot gases also in helical flow, means to separate and discharge the material tangentially of the envelope when dried, and means serving to extract the gases axially.

The drying apparatus may comprise a tubular vessel having at least one inlet disposed at or near one end for the material to be dried, at least one inlet at or near the same end for the heat delivering gases, means for continuously moving the material and gases within the tubular vessel about the axis thereof whereby the material and gases near said inlet continuously pass the gas inlet, and means for drawing 03 the gases and dried material separately at the other end of the tubular vessel whereby the material and gases are caused to describe a helical path through the vessel. Means may be provided for retain-= ing undried material within the vessel until the desired degree of drying has been attained.

Further features of the invention will be apparent from the following description with reference to the accompanying drawings, in which:

Fig. 1 is a longitudinal sectional elevation of one form of drying apparatus according to this invention.

Fig. 2 is aplan view, partly in section, the sectioned portion being online II-II of Fig. 1.

Fig. 3 is an end elevation looking in the direction of arrow A, Fig. l, and partly in section, the sectioned portion being on lines IIIIII of Figs. land 2.

Fig. 4 is a fragmentary sectional elevation taken on line IV-IV of Fig 3.

5 is a transverse sectional elevation taken on lines V-V of Figs. 1 and 6.

Fig. 6 is a fragmentary side elevation, partly in section, the sectioned portion being on line VI-VI of Fig. 5.

Fig. '7 is a fragmentary transverse sectional elevation taken on line VII-VII of Fig. 6.

Fig. 8 is a fragmentary transverse sectional elevation of a detail.

Figs. 9 and 10 are, respectively, a sectional elevation on line IXIX of Fig. 8, and a plan view of Fig. 8.

Figs. 11 and 12 are fragmentary sectional elevations of modified forms of a detail.

Fig. 13 is an elevation of a modified form of dryer.

Fig. 14 is a fragmentary sectional elevation of a further modified form of dryer.

The form of apparatus illustrated in Figs. 1 to 7 comprises a hollow cylindrical stationary vessel l arranged with its axis horizontal and provided with end plates 2 and 3 which substantially close the ends except as hereinafter described. A rotatable shaft 4 is disposed concentrically within and adapted to rotate in the vessel I, being supported in bearings 5 disposed outside the vessel I. Rotation of the shaft 4 is effected by a pulley 8 which is rotated by a belt I from a suitable drive source. A tubular sleeve 8 is mounted on the shaft 4 and within the vessel I, the said sleeve 8 being secured to the shaft 4 in any suitable manner so as to rotate therewith. A series of discs 8 are secured on the sleeve 8, suitably spaced apart, and a series of paddles III are pivotally mounted by means of arms l2 on axles i'l' disposed between and mounted in adjacent discs 8 with their axes parallel to the axis of the shaft 4. The arrangement of the paddles ill on the sleeve 8 issuch that when the shaft 4 *is rotated the paddles will be rotated within the vessel land the outer edges or tips of said paddles during such rotation'will be close to the inner surface of the vessel I. Preferably, the paddles disposed between one pair of discs 9 are angularly staggered in relation to the paddles disposed between an adjacent pair of discs. The blades [3 of a propeller are also secured to the sleeve 8 to sweep the end plate 2.

A mechanical material feeder l4, comprises as shown in Fig. 3 a hopper l5, and a feed worm I5 adapted to be rotated by means of a pulley i1 driven from the shaft 4 by a pulley l8 and belts l9 through a speed change device 20. The worm it, which charges. the material into the vessel i through an inlet 2|, terminates some distance before said inlet so as to build up between its end and the inlet a plug of material to form a gas seal.

The inlet 2| is preferably arranged so that the material charged into the vessel may enter substantially tangentially into the path of the pad-L end of the vessel they are preferably disposed in spaced relation on the periphery for example substantially diametrically opposed as shown in F18. 8.

The discs 3 and paddles l0 extend the major portion of the length of the vessel I from the inlet end plate 2. The paddles ID are hinged on the discs- 8 to form loose and swinging bodies or plates which can yield to any sudden resistance. Further, the paddles it can be positioned either parallel with the axle of the shaft 4 or at an angle thereby, so that in the latter case they can assist the forward movement of the material.

Particularly, for a purpose which will be stated, it is desirable that the sets of paddles nearer the end plate 2 should be inclined as shown in Fig. 2.

The gas inlet ports 22 may extend up to half of the length of the drying vessel swept by the paddles l0, and at the end of this length there is disposed an inwardly directed ring or shoulder 23 which constitutes a weir. v

A frusto-conical baiile plate 24 is disposed inside the vessel l projecting from the outlet end plate 3 aboutthe shaft 4 and sleeve 8 to afford an annular orifice at itscentre. The space between the baflle plate 24 and the end plate 3 forms a gas discharge chamber 26 in communication with a fan 21 through a conduit 28 and an opening 23 in the end plate 3. I

Fan 21, which discharges to a chimney 10, may be driven as shown by a pulley 30 on shaft 4, a belt 3|, and a pulley 32 on the fan shaft.

A disc 42 secured on the sleeve 8 has a coaxial ring 45 fixed to and spaced from it by a series of vanes 69 (Figs. 1 and 5) and a series of paddles 43 are pivotally mounted on axles 44 supported by said disc and ring.

The space between the weir 23 and the disc 42 on the one side and the conical baflle plate 24 on the other side constitutes a separating chamber dles l0 which rotate in the direction of the ar-, row B. The inlet 2! is disposed close to the inlet end plate 2, as shown in Figs. 2 and 4.

Hot gas. inlet ports 22 are located near, or ex-f 5:

tending very near the inlet end plate 2; and are arranged as shown in Fig. 3 to direct gases en-v tering through them chordally to the movement of the paddles "I. These ports 22 are connected.

outside the drying vessel i with a common flue (not shown) to which hot gases from a suitable from the feed hopper i5 is propelled intothe vessupply source, such as a combustion furnace, semi gas producer or gas producer plant, or heat exchanger are supplied.

Though the inlets 2i and 22 respectively for material to be dried and hot gases are at the same their quantity and reduce their temperature.

33 access to which is afforded by the annular opening between the inner edge of the weir 23 and the outer edge of the disc 42.

The dried material discharge slots 34 open through the shell of the vessel I into a discharge box 35 formed outside of the vessel, and having attached to it. a discharge chute 36, a worm 31 mounted in the bottom of the box 35 being adapted to propel the material to the chute 36 under rotation by a'pulley 38 on the shaft 4, a

belt 39 and a pulley 40 on the worm shaft 4|.

As shown in Figs. 6 and 7, the top part of the box 35 has a branch 41 leadin tangentially back into the drum l in front of the weir 23.

Preferably the paddles I0 incline towards the direction of rotation, as shown in Fig. 3, whereas the paddles 43 may incline away from the direc tion of rotation as. shown in Fig. 5.

In operation, the shaft 4 is caused to rotate -rapidly,-and drivesthe feed worm 16, the fan 21 and the discharge worm 31.

. Thefan 2' lcre'ates' a sub atmospheric pressure ii'i'thesvesseli; 1 to be sucked intothewessel through the ports- :and heat delivering gases 22 as high velocity, jets.

Bimtt'ltaneously heat absorbing wet material sel by the feed worm l6. I

By contact between the gases and material immediateevaporationof' some of the water content of the material is effected and the steam evolved mixes with the gas inside the vessel to increase Under the rotation of the paddles Ill the gases carry the material round inside of the vessel dried material;

shown the heat-delivering gases are distributed" to constitute a hot zone of high and substantially even temperature, in which the heat absorbed by evaporation of moisture is balanced by continual access of heat-delivering gas so long as the carrier gases and material continue to cross the inlets 22.

In this way the temperature of the jets of heat delivering gas, which may be very high, is lowered to the average temperature of the hot zone in the immediate vicinity of their entrance. Even in cases where the material to be dried can tolerate only a comparatively low temperature, the hot delivering gases can be introduced at a very high temperature, and the temperature of the carrier gases in the hot zone can be regulated by the volume of hot gases introduced throughout this zone. a

Only at the end plane of the hot zone, that is, at the end of the inlets 22, remote from the end plate 2, is the full quantity of heat-delivering gases flowing axially in the vessel I. From this is progressively less, and consequently the axial speed is slower. Accordingly the axial movement of the carrier gases and the material is assisted by the inclination of the paddles iii.

The portion of the vessel i from said end plane of the inlets 22 to the weir 23 constitutes a zone of falling temperature in which the drying of the material is completed.

The material is swept round the inside of the vessel i by the paddles in a layer, under centrifugal force, and the thickness of this layer, and thus the period during which it is retained in said zone is determined by the depth of the weir 23. The latter may be interchangeable with other weir rings of difierent widths to vary the thickness of the'layer of material.

-.-- -.a- ,rThe dried material is separated from more moist material by reason that the wetter and, therefore, heavier elements are forced centrifug'ally outwards whilst the lighter drier elements are displaced towards the inner surface of the layer. Thus, only the dried and lightest elements can be displaced by the carrier gases under the influence of the fan 21 over the inner edge of the weir 23 and drawn into the separating chem ber 83.

In this way the weir 23 not only has the function of controllin the drying time but also efiects plane back to the end plate 2 the quantity of gas slots and to-the drum. This gas flow through the, slots" acilitatesthe passage of the The discharged material settles down at the bottom of the box]! and is expelled by the worm 31 to the discharge'chute 36. As the worm ends at a distance before the chute 36 the material forms a plug which serves as a gas seal.

The inner surface of the drying vessel can be either smooth for products where a crushing of the material to be dried is undesirable or the inner surface may be provided with cutters projecting inwardly which are provided with sharpened edges facing the direction of movement of the arms and the material.

As shown in Figs. 8, 9 and 10 cutters-48 are provided around the periphery of the vessel, the

paddles l0 being slotted at 49 at their outer edges to allow them to pass-the cutters. The material to be dried is out between the paddles Ill and the cutters 48 so that fresh wet surfaces of the materlal are continually exposed as the drying proceeds. Preferably, the cutters are disposed towards the end of the drying zone, that is, to co-operate with the paddles adjacent the weir 43, see Fig. 9. Conveniently the cutters 48 may be mounted in sets on plates 50 adapted to be inserted in openings in the casing I, so that said cutters may be easily renewed when necessary.

In the modification shown in Fig. 11 the weir is formed as a conical ring 5!, which may be made in segmentalporti-ons, isprovided with bosses 52 having screwed holes 53 and is secured by bolts 54 screwed from the outside of the vessel into the bosses '52. By providing rings iii of different internal diameters, and fixing an appropriate one ;in the vessel, the depth of the weir may be ad- Justed. In an alternative arrangement, shown in Fig. 12, the conical weir ring 5i. is made of thin flexible and resilient material and is slotted laterally at 55 from the free edge to form leaves as which overlap each other; pins 56, mounted on a ring 5], project through slots 58 into the vessel and engage'the undersides of the leaves 65; the ring 51 may be moved longitudinally of the vessel by means of adjusting bolts 59 in screw-thread engagement with a fixed ring 66 so that the leaves may be moved towards or away from the axis of the vessel and so adjust the depth of the weir.

In the modified form of apparatusshown in Fig. 13, the vessel I is gradually reduced in diameter, or conically formed, at 60, throughout the zone of falling temperature. Such conical forma tion of the vessel serves the purpose of a weir to effect the separation of the dry material from wet material.

In order to expel heavy and hard foreign bodies such as iron, stones, sand and the like which may enter the drying vessel a stone trap Si is provided at its lowest point near but before the weir. This position is chosen on account of the fact that near the weir the material is already substantially dry, and the foreign bodies which are of much greater weight easily work down to the bottom of the trap. The trap may be provided with a door or flap 62 controlled in known manner by a spring or counter-weight means not shown so that as soon as the weight of bodies in the trap exceeds a certain predetermined amount the door will open and allow the foreignbodies to fall out after which the door automatically closes. v i

In the modified arrangement illustrated in Fig. 14 a fan impellertii is mounted on the sleeve 8 on the shaft 4, the fan chamber G'Ibeing formed by an end wall 68 and a plate 64 substantially parallel thereto which is orificed axially to provide the annular orifice 25 around the shaft 4 for the passage of exhaust gases from the separating chamber 33 to the fan chamber 61. The said fan is of the same or larger diameter than the separating chamber 83 in order to produce the necessary draught, and has an exhaust branch 10.

As the shaft 4 may overheat near the inlet end the sleeve 8 may be annularly 'spaced from the shaft as shown in Fig. 1, one end of the sleeve projecting through the end plate 2 and the other end opening into the gas discharge chamber 26 or the fan chamber 61 where there is a sub-atmospheric pressure by which a continuous flow of cooling air is inducedfrom the atmosphere through the annular space,

The self-contained plant described may be mounted on a self-propelled vehicle or on a separate chassis to be drawn by a tractor, and, therefore, easily moved 'to any desired position.

As the heat delivering gases can be combustion gases at a very high temperature and practically free of excess air the volume of heat demum temperatures permissible for the treatment of different materials.

Consequent upon, the compact form of the dryer, its relatively small outersurface compared with its capacity, the small volume of heat delivering gases required and the small chimney losses, the thermal efficiency of the device is raised to the highest level. As many substances to-be dried have to be treated in an atmosphere free of oxygen such substances can be dried in this apparatus with great advantage. The gases escaping from the plant have a very high partial pressure of steam and are therefore useful.

With apparatus according to the present in: vention the continuous crushing of the material to be dried, thus expos' fresh wet surfaces, the high relative speed bet en thecarrier gas and the material being dried and the high turbulence within the vessel, thejdryingtime is reduced to a minimum. The dryer is suitable for treatment of a large range of materials also including sticky paste-like material or liquids of high or low viscosity, as the whole surface of the dryer'is mechanically swept on the inside and particles sticking to the walls are constantly cleared. Owing to the simplicity of the construction the cost of the dryer is very low compared with known drying apparatus having equivalent output capacity.

What I claim and desire to secure by Letters Patent is: I

1. A concurrent flow dryer for drying mateture disposed adjacent the axis of said casing at said other end, and rotary separator means rials by means of hot gases, comprising a .sta-' tionary casing of substantially circular crosssection, means for feeding material to be dried ducing hot drying gases in the vicinity of that end, rotary means within said casing applying rapid rotational impulsion to said material and gases to cause said material and gases to gyrate adjacent the inner surface of said casing, and

into one end of said casing, means for introapplying centrifugal impulsion to said dried material to separate it from the gases flowing radially inwards to said withdrawal aperture and to discharge saidmaterial tangentially through said materialdischarge aperture.

2. A concurrent flow dryer for drying materials by means of hot gases, comprising a stationary casing of substantially circular crosssection, means for feeding material to be dried into one end of said casing, means for introducing hot drying gases in the vicinity of that end, rotary means within said casing applying rapid rotational impulsion to said material and gases to cause said material and gases to gyrate acUacent the inner surface of said casing, and gas transporting means imparting to the gyrating gases and material an endwise impulsion along said inner surface with resultant helical motion, in combination with internal separating means adjacent the other end of the casing for the gases and the dried material comprising a disc disposed transversely to afford a restricted opening between its circumferential edge and said inner surface for theendwise passage of dried material and gases, a material discharge aperture in the periphery of the casing between the plane of said disc and said other end of said casing, a gas withdrawal aperture disposed adjacentj the axis of said casing at said other end, and rotary separator means applying centrifugal impulsion tosaid dried material to separate it from the gases flowing radially inwards to said withdrawal aperture and to discharge said material tangentially through said material discharge aperture.

3. A concurrent fiow dryer for drying materials by means of hot gases, comprising a sta tionary casing of substantially circular crosssection, means for feeding material to be dried into one end of said casing, means for introducing hot drying gases in the vicinity of that end, rotary means within said casing applying rapid rotational impulsion to said material and gases to cause said material and gases to gyrate adjacent the' inner surface of said casing, and gas transporting means imparting to the gyrating gases and material an endwise impulsion along said inner surface with resultant helical motion, in combination with internal separating means adjacent the other end of the casing for the gases and the dried material comprising a means having a disc disposed. transversely to afford a restricted opening between its circumferential edge and said inner surface for the endwise passage of dried material and gases to the zone of said material discharge aperture,

. said disc carrying impeller means applying centrifugal impulsion tosaid dried material to separate it from'the gases flowing radially in- -.wards to said withdrawal aperture and to discharge said material tangentially through said 'm'aterial discharge aperture.

4. A concurrent flow dryer for, drying materials by means of hot gases, having a stationary casing of substantially circular cross-section, one end of the casing being a feed end and the other end thereof being a discharge end, and

with internal separating means for gases and dried material adjacent said discharge end, comand gas transporting means imparting to the 8 gyrating material and gases an endwise impuision along said inner surface with resultant helical motion, said internal separating means comprising a material discharge aperture in the periphery of said casing, a gas withdrawal aper- 1C ture atthe centre of the discharge end of the casing, and rotary separator means applying centrifugal impulsion to said dried material for separating it from the gases flowing radially inwards to said withdrawal aperture and for dis- 1| charging said material tangentially through said peripheral aperture.

5. A concurrent flow dryer for drying materials by means of hot gases, having a stationary casing of substantially circular cross-section, one end of a the casing being a feed end and the other end thereof being a discharge end, and with internal separating means for gases and dried material adjacent said discharge end, comprising rotary means within said casing applying to said material as and gases rapid rotational impulsion to cause said material and gases to gyrate adjacent the inner surface of said casing, and gas transporting means imparting to the gyratingmaterlal and gases an endwise impulsion along said inner surg face with resultant-helical motion, said internal separating means comprisin a material discharge aperture in the periphery of said casing, a gas withdrawal aperture adjacent the axis of said casing at said discharge end, and rotary separator means applying centrifugal impulsion to said dried. material for separating it from the gases flowing radially inwards to said withdrawal aperture and for discharging said material tangentially through said peripheral aperture, i 40 material'comprising a material discharge apercombination with an annular weir projecting radially inwards from the inner surface of the casing and located at the side of said separating means farther from said discharge end,

6. A concurrent flow dryer for drying materials by means of hot gases, having a stationary casing of substantially circular cross-section, one end of the casing being afeed end and the other end thereof being a discharge end, and with internal separatin means for gases and dried material adjacent said discharge end, comprising rotary means within said casing applying to said material and gases rapid rotational impulsion to cause said material and gases to gyrate adjacent the,

inner surface of said casing, and gas transporting means imparting to the gyrating material and gases an endwise impulsion along said inner surface with resultant helical motion, said internal separating means comprising a material discharge aperture in the periphery of said casing, a gas so to said dried material for separating it from the gases flowing radially inwards to said withdrawal aperture and for discharging said material tangentially through said peripheral aperture, in combination with an annular weir projecting.

radially inwards from the inner surface of the casing in a plane adjacent the plane of said disc, the inner edge of said annular weir and the outer edge of said disc jointly defining a restricted opening for the endwise passage of dried material and gases to said separating means.

surface of said casing, and gas transporting means imparting to the gyrating material and gases an endwise impulsion along said inner surface with resultant helical motion, said internal separating means comprising a material discharge aperture in the upper part of the periphery of said casing, a gas withdrawal aperture in the discharge end member of the casing, a transverse plate within the casing and spaced apart from said end member, said transverse plate having a central opening, and rotary separator means applying centrifugal impulsion to said dried material for separating it from the gases flowing radially inwards to said central opening and thence to said withdrawal aperture and for discharging said materialv tangentially through said peripheral aperture.

8. A concurrent flow dryer for drying materials by means of hot gases, comprising a stationary casing of substantially circular cross-section,

means for feeding material to be dried into one end of said casing, means for introducing hot gases in the vicinity of that end, rotary means within said casing applying to said material and gases rapid rotational impulsion to cause said material and gases to gyrate adjacent the inner surface of, said casing in combination with internal centrifugal separating means adjacent the other end of the casing for the gases and the dried ture in the periphery of said casing, a transverse end plate of the casing, a transverse plate with a central opening spaced inwardly from said end plate to form within the casing a gas discharge chamber, a fan impeller mounted coaxially within said chamber, said impeller constituting gas transporting means imparting to the gyrating gases and material an endwise impulsion along I a the irmer surface of said casing with resultant helical motion, a tangential gas outlet from said chamber, and rotary separator means applying centrifugal impulsion to said dried material to separate it from the gases flowing radially in-- wards to said central opening and to discharge said material tangentially through said material discharge aperture.

9. A concurrent flow dryer for drying materials by means of hot gases, comprising a stationary casing of substantially circular cross-section, one end of the casing being a feed end and the other end thereof being a discharge end, rapid rotary means within said casing, gas transporting means in communication with said casing, an annular weir projecting radially inwards from the inner surface of the casing, said weir being constituted by a ring of frusto-conical shape which reduces the diameter of the casing in the direction of endwise movement of .the gyrating material and gases, and located at a lesser distance from the discharge end than from thefeed end of the casing, and centrifugal separating means disposed between said weir and said discharge end.

10. A concurrent flow dryer for drying materials by means of hot gases, comprising a stationary casing of substantially circular crosssection, one end of the casing being a feed end and the other end thereof being a. discharge end, rapid rotary means within said casing, gas transporting means in communication with said casing, an annular weir projecting radially inwards from the inner surface of the casing, said weir being constituted by elements forming a frustoconical ririg and movable by variation of their slope, abutments on the casing bearing on said elements and being displaceable to vary said slope and thereby adjust the radial depth of the weir, said frpsto-conical ring being located at a lesser distance from the discharge end than from the feed end of the casing and centrifugal separating means disposed between said weir and said discharge end.

ii. A concurrent flow dryer for drying materials by-ineans of hot gases, comprising a stationary casing of substantially circular cross-section, means for feeding material to be dried into one end of said casing, means for introducing hot drying gases in the vicinity of that end, rotary means operable within said casing at high speed to apply to said material and gases rotational impulsion to cause said material and gases to gyrate adjacentthe inner surface of said casing, and gas transporting means imparting to the gyrating gases and material an endwise impulsion along said inner surface with resultant helical motion, in combination with internal centrifugal separating means adjacent the other end of the casing for the gases and the dried material comprising a material discharge aperture in the periphery of said casing, a gas withdrawal aperture disposed adjacentthe axis in the other end of the casing, and rotary separator means applying centrifugal impulsion to said dried material to separate it from the gases flowing radially inwards to said withdrawal aperture and to discharge said material tangentially through said material discharge aperturera discharge box disposed outside the casing to receive dried material discharged through saidr material discharge aperture, and a discharging device located in the lowest part of said discharge box, said discharge box forming a settlingchamber and said discharging device forming a g'as seal for said discharge box under pressure created by the rotary separator.

12. A concurrent flow dryer for drying materials by means of hot gases, comprising a stationary casing of substantially circular cross-section.

means for-feeding material to be dried into one end oi'ajsaid casing, means for introducing hot drying gases in the vicinity of that end, rotary means within said casing applying to said material and gases rapid rotational impulsion to cause said material and gases to gyrate adjacent the inner surface of said casing, and gas transporting means imparting to the gyrating gases and material an endwise impulsion along said inner surface with resultant helical motion, in'comblnation with internal separating means adjacent the other end of the casing for the gases and the dried material comprising a material discharge aperture in the periphery of said casing, a gas withdrawal aperture disposed adjacent the axis in said other end of the casing, and rotary separator means, having a disc disposed transversely to afford a restricted opening between its circumferential edge and said inner surface for the endwise passage of dried material to the zone of said material discharge aperture, said disc carrying impeller means applying centrifugal impulsionto said dried material to separate it from the gases flowing radially inwards to said withdrawal aperture and to discharge said material tangentially through said material discharge aperture, a discharge box disposed outside the casing to receive dried material discharged through said material discharge aperture, a discharging device located in the lowest part of said discharge box, said discharge box forming a settling chamhot drying gases in the vicinity of that end, rotary means carried by a shaft rotatable at high speed within said casing to apply to said material and gases rapid rotational impulsion to cause said material and gases to gyrate adjacent the inner surface of said casing, and gas transporting means imparting to the gyrating gases and material an endwise impulsion along said inner surface with resultant helical motion, in combination with internal separating means adjacent the other end of the casing for the gases and the dried material comprising a material discharge aperture in the periphery of said casing, a gas withdrawal aperture disposed adjacent the axis in said other end of the casing, and rotary separator means including a disc mounted transversely on said shaft to afford a restricted opening between its circumferential edge and said inner surface for the endwise passage of dried material to the zone of said material discharge in aperture, said disc carrying impeller means applying centrifugal impulsion to said dried material to separate 'it from the gases flowing radially inwards to said withdrawal aperture and to discharge said material tangentially through said material discharge aperture, said shaft comprising a tubular sleeve and an inner the sleeve being spaced from the ax e member to form an annular duct, one end of said duct being open to the external atmosphere and the other end open to the interior of the casing adjacent said gas withdrawal aperture to enable cooling air to flow through the duct.

14. A concurrent flow dryer for drying materials by means of hot gases, comprising a stationary casing of substantially circular cross-section, one endof the casing being a feed end and the other end thereof being a discharge end, a rotary gases an endwise impulsion, in the effectively annular spacebetween' said inner surface and the edges of said discs with resultant helical motion of saidmaterial and gases, an annular weir projecting radially inwards from the inner surface of the casing, said weir being located at a lesser distance from thedischarge end than from the feed end of the casing, and centrifugal separating xle member,

means disposed between said weir and said discharge end.

15. A concurrent flow dryer for drying material by means of hot gases, comprising a stationary casing of substantially circular cross-section, means for feeding material to be dried into one end of said casing, means for introducing hot drying gases in the vicinity of that end, a bladed rotor within said casing adapted to be rotated rapidly for applying rapid rotational impulsion to the material and gases to effect gyration thereof adjacent the inner surface of said casing, gas transporting means imparting to the gyrating material and gases an endwise propulsion along said inner surface with resultant helical motion, an annular weir projecting radially inwards from the inner surface of said casing adjacent the rotor end opposite to that at which the material and gases are introduced, a plurality of cutters located adjacent said weir, saidcutters projecting radially inward from the'inner surface of said casing and being received in correspondingly positioned slots in the rotor blades, and centrifugal separating means for the dried material and gases disposed inside of said casing at the side of said weir opposite to that on which said cutters are located, said separating means including a material discharge aperture in the periphery of said casing, a gas withdrawal aperture disposed adjacent the axis of said casing, and rotary separator means for applying centrifugal impulsion to said dried material.

OSWALD HELLER.

1 14 narnnnncas man The following references are of record in the file of this patent:

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